The present invention relates to an automatic door closer with a closer shaft adapted to be connected to a door, and in which the closer shaft is turnably mounted in the region of the one end of an elongated housing in opposite directions from a position in which the door is closed. A cam disk is connected within the fluid-filled housing to the closer shaft for turning therewith, and this cam disk cooperates, by means of rollers fixed to a longitudinally movable slide, to move the latter in the longitudinal direction of the housing during turning of the door in either direction from the closed position. The slide is connected to a piston of a hydraulic damping arrangement and a spring arrangement forming an energy storage. The piston divides the interior of the housing into two pressure spaces which are connected to each other by channels for the throttled flow of the pressure medium from one pressure space, the volume of which is reduced during closing of the door, into the other pressure space.
With a door closer of the aforementioned type, which may be constructed as a closer mounted in an appropriate cavity in the floor, an automatic closing of the door will be obtained after each opening of the same, since the pressure medium can flow through the aforementioned channels from the pressure space, the volume of which is reduced during closing of the door, back into the other pressure space, in which the spring arrangement providing the closing force is arranged. This known door closer is provided forwardly and rearwardly of the piston with two channels, offset in the longitudinal direction of the housing, in which throttle devices are arranged through which the backflow speed of the pressure fluid from one pressure space into the other may be regulated. Thereby it is possible to dampen the first phase of the closer movement of the door to a lesser degree than the second phase of the door closing movement, so that the door will be moved without impact by the return spring to the closed position. During the opening movement of the door, the action of the throttle channels will be obviated by arranging a one-way valve in the piston which provides communication between the two pressure spaces during the closing movement of the door. However, the force of the closing spring must be overcome during the opening movement of the door. Especially at so-called fire doors which during existence of a fire have to be moved to a closed position, it is desirable that the door, during normal conditions, be easily movable, as a door without door closer, so that the door may be moved also by children without danger.